"Jet" <thatjetnospam at yahoo.com> wrote in message
news:3D353D8F.8A736C4B at yahoo.com...
>>> Bob LeChevalier wrote:
> >
> > "John Knight" <johnknight at usa.com> wrote:
> > >Believe me, Parse, you don't need algebra or calculus to calculate the
> > >statistical average for American girls in TIMSS math. Even adjusting
for
> > >guesses doesn't require anything but some very basic probability
theory.
> > >
> > >It's as simple as this:
> > >
> > >If you're asked a question which has four multiple choice answers, and
you
> > >haven't got a clue what the answer is, what is the probability of
getting a
> > >correct answer? Since you have once chance in four of getting the
right
> > >answer, your probability is 0.25. If you guess on two questions, your
> > >probability is .5, and three it's .75, and four, it's 1.0.
> > >
> > >In other words, over the long run, or over millions of test takers,
guessing
> > >on such a question will yield 25% correct answers, or conversely, every
> > >fourth answer will be correct.
> >
> > This makes the assumption that those who know nothing guess randomly.
IN
> > reality, we don't know that people guess randomly when faced with a test
> > question they do not understand. Indeed, we know that they do not.
> >
Wrong. Dead wrong. You could make that argument about one question, but
when the pattern is repeated over and over again, then you can detect a
pattern: American girls scored lower on many questions than if they'd just
guessed because they didn't have a clue about what the answer was. Many of
these questions had zero misses [read: 0% failed to provide an answer at
all], which means you're nuts to even hint that "Indeed, we know that they
do not" "guess randomly".
The ONLY time you could apply that argument is when a large percentage of
them answered correctly, but even then, if 0% failed to respond at all, then
some of them HAD to guess.
> > But the assumption becomes totally meaningless if in fact they know
> > SOMETHING. If 100% of them know something, but not enough to solve the
> > problem, then it is quite plausible that 100% of them will get the
answer
> > wrong. Thus someone knowing Newtonian physics perfectly will get the
wrong
> > answer on a question that uses special relativity theory. A good test
> > designer will know that the Newtonian approximation is a likely error,
and
> > will include that answer among the incorrect alternatives.
>> Then the article makes the shockingly stupid conclusion that NONE of the
> girls who got the answer right understood the problem!
>
If guessing on a multiple choice question would yield 25% correct, but
American girls only got 5% correct, then how would YOU calculate how many of
them understood the problem?
> >
> > >No algebra. No calculus. A bit of probability theory, and you already
know
> > >that 25% of all students will get the correct answer if they only
*guess* on
> > >a four part multiple choice question.
> >
> > But you have no evidence that any kid "guessed" on any problem.
> >
> > >Now here's the hard part:
> > >
> > >Question H04 on TIMSS had four multiple choice answers, so you would
think
> > >that no country or age group or race or sex would answer less than 25%
of
> > >them correct, right?
> >
> > Wrong. I would think that if the question were difficult and well
designed,
> > that this would be quite possible.
> >
> > >How do you think that's possible?
> > >
> > >You can probably figure this out with no knowledge of algebra or
calculus,
> > >and you already know all the probability theory that might be needed,
so
> > >what is your explanation?
> >
> > I've given an explanation, and mine explains how on question D12, both
boys
> > and girls in the US scored less than 17% and South Africans scored only
6.4%
> > correct.
>> Isn't it odd that someone who is harping on math ability doesn't seem to
> realize that 17 and 6 are both lower than 25? :)
>> J
What's your point, J? Who exactly do you think made the point that getting
17% correct on a four part multiple guess problem is a lower score than if
everyone just guessed?
What part of that don't you understand (other than the typical and
infinitely STUPID statement by lojbab that no students guessed)?
John Knight
